ASTM G177-03(2008)e1
(Specification)Standard Tables for Reference Solar Ultraviolet Spectral Distributions: Hemispherical on 37° Tilted Surface
Standard Tables for Reference Solar Ultraviolet Spectral Distributions: Hemispherical on 37<span class='unicode'>°</span> Tilted Surface
SIGNIFICANCE AND USE
This standard does not purport to address the mean level of solar ultraviolet spectral irradiance to which materials will be subjected during their useful life. The spectral irradiance distributions have been chosen to represent a reasonable upper limit for natural solar ultraviolet radiation that ought to be considered when evaluating the behavior of materials under various exposure conditions.
Absorptance, reflectance, and transmittance of solar energy are important factors in material degradation studies. These properties are normally functions of wavelength, which require that the spectral distribution of the solar flux be known before the solar-weighted property can be calculated.
The interpretation of the behavior of materials exposed to either natural solar radiation or ultraviolet radiation from artificial light sources requires an understanding of the spectral energy distribution employed. To compare the relative performance of competitive products, or to compare the performance of products before and after being subjected to weathering or other exposure conditions, a reference standard solar spectral distribution is desirable.
A plot of the SMARTS2 model output for the reference hemispherical UV radiation on a 37° south facing tilted surface is shown in Fig. 1. The input needed by SMARTS2 to generate the spectrum for the prescribed conditions are shown in Table 2.
SMARTS2 Version 2.9.2 is required to generate AM 1.05 UV reference spectra.
The availability of the adjunct standard computer software (ADJG0173CD ) for SMARTS2 allows one to (1) reproduce the reference spectra, using the above input parameters; (2) compute test spectra to attempt to match measured data at a specified FWHM, and evaluate atmospheric conditions; and (3) compute test spectra representing specific conditions for analysis vis-à-vis any one or all of the reference spectra.
SCOPE
1.1 The table provides a standard ultraviolet spectral irradiance distribution that maybe employed as a guide against which manufactured ultraviolet light sources may be judged when applied to indoor exposure testing. The table provides a reference for comparison with natural sunlight ultraviolet spectral data. The ultraviolet reference spectral irradiance is providded for the wavelength range from 280 to 400 nm. The wavelength region selected is comprised of the UV-A spectral region from 320 to 400 nm and the UV-B region from 280 to 320 nm.
1.2 The table defines a single ultraviolet solar spectral irradiance distribution:
1.2.1 Total hemispherical ultraviolet solar spectral irradiance (consisting of combined direct and diffuse components) incident on a sun-facing, 37° tilted surface in the wavelength region from 280 to 400 nm for air mass 1.05, at an elevation of 2 km (2000 m) above sea level for the United States Standard Atmosphere profile for 1976 (USSA 1976), excepting for the ozone content which is specified as 0.30 atmosphere-centimeters (atm-cm) equivalent thichkness.
1.3 The data contained in these tables were generated using the SMARTS2 Version 2.9.2 atmospheric transmission model developed by Gueymard (1,2).
1.4 The climatic, atmospheric and geometric parameters selected reflect the conditions to provide a realistic maximum ultraviolet exposure under representative clear sky conditions.
1.5 The availability of the SMARTS2 model (as an adjunct (ADJG0173CD )to this standard) used to generate the standard spectra allows users to evaluate spectral differences relative to the spectra specified here.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: G177 − 03 (Reapproved2008)
Standard Tables for
Reference Solar Ultraviolet Spectral Distributions:
Hemispherical on 37° Tilted Surface
This standard is issued under the fixed designation G177; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—The title to Table 2 was corrected editorially in August 2008.
INTRODUCTION
These tables of solar ultraviolet (UV) spectral irradiance values have been developed to meet the
need for a standard ultraviolet reference spectral energy distribution to be used as a reference for the
upper limit of ultraviolet radiation in the outdoor weathering of materials and related indoor exposure
studies.Awide variety of solar spectral energy distributions occur in the natural environment and are
simulatedbyartificialsourcesduringproduct,material,orcomponenttesting.Tocomparetherelative
opticalperformanceofspectrallysensitiveproducts,ortocomparetheperformanceofproductsbefore
and after being subjected to weathering or other exposure conditions, a reference standard solar
spectral distribution is required. These tables were prepared using version 2.9.2 of the Simple Model
oftheAtmosphericRadiativeTransferofSunshine(SMARTS2)atmospherictransmissioncode (1,2).
SMARTS2 uses empirical parameterizations of version 4.0 of theAir Force Geophysical Laboratory
(AFGL) Moderate Resolution Transmission model, MODTRAN (3,4). An extraterrestrial spectrum
differing only slightly from the extraterrestrial spectrum in ASTM E490 is used to calculate the
resultant spectra. The hemispherical (2π steradian acceptance angle) spectral irradiance on a panel
tilted 37° (average latitude of the contiguous United States) to the horizontal is tabulated. The
wavelengthrangeforthespectraextendsfrom280to400nm,withuniformwavelengthintervals.The
input parameters used in conjunction with SMARTS2 for each set of conditions are tabulated. The
SMARTS2 model and documentation are available as an adjunct ADJG173CD ) to this standard.
1. Scope 1.2 The table defines a single ultraviolet solar spectral
irradiance distribution:
1.1 The table provides a standard ultraviolet spectral irradi-
1.2.1 Total hemispherical ultraviolet solar spectral irradi-
ance distribution that maybe employed as a guide against
ance (consisting of combined direct and diffuse components)
which manufactured ultraviolet light sources may be judged
incident on a sun-facing, 37° tilted surface in the wavelength
when applied to indoor exposure testing. The table provides a
regionfrom280to400nmforairmass1.05,atanelevationof
reference for comparison with natural sunlight ultraviolet
2 km (2000 m) above sea level for the United States Standard
spectral data. The ultraviolet reference spectral irradiance is
Atmosphere profile for 1976 (USSA 1976), excepting for the
provided for the wavelength range from 280 to 400 nm. The
ozone content which is specified as 0.30 atmosphere-
wavelength region selected is comprised of the UV-Aspectral
centimeters (atm-cm) equivalent thickness.
region from 320 to 400 nm and the UV-B region from 280 to
320 nm.
1.3 The data contained in these tables were generated using
the SMARTS2 Version 2.9.2 atmospheric transmission model
developed by Gueymard (1,2).
ThesetablesareunderthejurisdictionofASTMCommitteeG03onWeathering
1.4 The climatic, atmospheric and geometric parameters
and Durability and is the direct responsibility of Subcommittee G03.09 on
Radiometry. selected reflect the conditions to provide a realistic maximum
Current edition approved June 1, 2008. Published August 2008. Originally
ultraviolet exposure under representative clear sky conditions.
e1
approved in 2003. Last previous edition approved in 2003 as G177–03 . DOI:
10.1520/G0177-03R08E01.
1.5 The availability of the SMARTS2 model (as an adjunct
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof 3
(ADJG173CD ) to this standard) used to generate the standard
this standard.
spectra allows users to evaluate spectral differences relative to
Available from ASTM International Headquarters. Order Adjunct No.
ADJG173CD. Original adjunct produced in 2005. the spectra specified here.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G177 − 03 (2008)
TABLE 2 Standard Ultraviolet Hemispherical Spectral Solar Irradiance for 37° Sun-Facing Tilted Surface
Wavelength Hemispherical Wavelength Hemispherical Wavelength Hemispherical Wavelength Hemispherical Wavelength Hemispherical
2 2 2 2 2
nm W/m /nm nm W/m /nm nm W/m /nm nm W/m /nm nm W/m /nm
λ E λ E λ E λ E λ E
λ λ λ λ λ
280.0 2.320E-16 307.5 0.1277 335.0 0.6826 362.5 0.7823 390.0 0.9986
280.5 2.453E-15 308.0 0.1334 335.5 0.6628 363.0 0.8033 390.5 1.0061
281.0 7.972E-15 308.5 0.1406 336.0 0.6063 363.5 0.7799 391.0 1.0646
281.5 9.229E-14 309.0 0.1334 336.5 0.5615 364.0 0.8065 391.5 1.0788
282.0 4.085E-13 309.5 0.1310 337.0 0.5517 364.5 0.7979 392.0 0.9923
282.5 1.081E-12 310.0 0.1482 337.5 0.5914 365.0 0.8274 392.5 0.8262
283.0 2.948E-12 310.5 0.1867 338.0 0.6325 365.5 0.9094 393.0 0.5975
283.5 4.660E-12 311.0 0.2288 338.5 0.6587 366.0 0.9729 393.5 0.4747
284.0 3.901E-11 311.5 0.2283 339.0 0.6684 366.5 0.9732 394.0 0.6162
284.5 8.723E-11 312.0 0.2380 339.5 0.6836 367.0 0.9539 394.5 0.8493
285.0 1.794E-10 312.5 0.2420 340.0 0.7261 367.5 0.9349 395.0 1.0022
285.5 5.618E-10 313.0 0.2564 340.5 0.7226 368.0 0.8791 395.5 1.0667
286.0 1.452E-09 313.5 0.2608 341.0 0.6754 368.5 0.8720 396.0 0.9371
286.5 5.743E-09 314.0 0.2768 341.5 0.6697 369.0 0.9103 396.5 0.6807
287.0 1.354E-08 314.5 0.2842 342.0 0.6968 369.5 0.9767 397.0 0.5268
287.5 3.518E-08 315.0 0.2926 342.5 0.7212 370.0 0.9889 397.5 0.7774
288.0 1.168E-07 315.5 0.2604 343.0 0.7314 370.5 0.8928 398.0 1.0521
288.5 2.398E-07 316.0 0.2589 343.5 0.6903 371.0 0.9057 398.5 1.2416
289.0 5.837E-07 316.5 0.3026 344.0 0.5971 371.5 0.9402 399.0 1.3169
289.5 1.539E-06 317.0 0.3446 344.5 0.5718 372.0 0.8791 399.5 1.3562
290.0 3.403E-06 317.5 0.3693 345.0 0.6476 372.5 0.8365 400.0 1.3701
290.5 6.192E-06 318.0 0.3463 345.5 0.6883 373.0 0.8046
291.0 1.192E-05 318.5 0.3480 346.0 0.6704 373.5 0.7244
291.5 2.602E-05 319.0 0.3733 346.5 0.6813 374.0 0.7217
292.0 4.777E-05 319.5 0.3699 347.0 0.6915 374.5 0.7155
292.5 6.429E-05 320.0 0.3889 347.5 0.6665 375.0 0.7626
293.0 1.052E-04 320.5 0.4423 348.0 0.6623 375.5 0.8425
293.5 2.055E-04 321.0 0.4323 348.5 0.6724 376.0 0.8716
294.0 3.080E-04 321.5 0.4091 349.0 0.6464 376.5 0.8568
294.5 4.169E-04 322.0 0.3969 349.5 0.6627 377.0 0.9181
295.0 6.400E-04 322.5 0.3863 350.0 0.7307 377.5 1.0232
295.5 1.137E-03 323.0 0.3664 350.5 0.7842 378.0 1.1015
296.0 1.650E-03 323.5 0.4085 351.0 0.7620 378.5 1.0727
296.5 2.088E-03 324.0 0.4483 351.5 0.7326 379.0 0.9559
297.0 2.489E-03 324.5 0.4682 352.0 0.7136 379.5 0.8563
297.5 3.984E-03 325.0 0.4748 352.5 0.6731 380.0 0.8990
298.0 5.347E-03 325.5 0.5390 353.0 0.7140 380.5 0.9619
298.5 5.899E-03 326.0 0.6128 353.5 0.7841 381.0 0.9772
299.0 7.299E-03 326.5 0.6400 354.0 0.8279 381.5 0.8794
299.5 0.0108 327.0 0.6287 354.5 0.8358 382.0 0.7485
300.0 0.0116 327.5 0.6121 355.0 0.8346 382.5 0.6466
300.5 0.0130 328.0 0.5744 355.5 0.8043 383.0 0.5788
301.0 0.0177 328.5 0.5860 356.0 0.7535 383.5 0.5597
301.5 0.0222 329.0 0.6486 356.5 0.7058 384.0 0.6469
302.0 0.0229 329.5 0.7136 357.0 0.6201 384.5 0.7779
302.5 0.0307 330.0 0.7201 357.5 0.6268 385.0 0.8530
303.0 0.0459 330.5 0.6647 358.0 0.5826 385.5 0.8141
303.5 0.0546 331.0 0.6283 358.5 0.5404 386.0 0.7846
304.0 0.0556 331.5 0.6420 359.0 0.6349 386.5 0.8148
304.5 0.0646 332.0 0.6560 359.5 0.7643 387.0 0.8213
305.0 0.0798 332.5 0.6540 360.0 0.8074 387.5 0.8086
305.5 0.0848 333.0 0.6413 360.5 0.7621 388.0 0.8000
306.0 0.0819 333.5 0.6154 361.0 0.7001 388.5 0.7935
306.5 0.0892 334.0 0.6275 361.5 0.6842 389.0 0.8606
307.0 0.1080 334.5 0.6615 362.0 0.7157 389.5 0.9529
2. Referenced Documents E772Terminology of Solar Energy Conversion
4 2.2 ASTM Adjuncts:
2.1 ASTM Standards:
ADJG173CD Simple Model forAtmospheric Transmission
E490Standard Solar Constant and Zero Air Mass Solar
of Sunshine
Spectral Irradiance Tables
3. Terminology
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.1 Definitions—Definitions of terms used in this specifica-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tion not otherwise described below may be found inTerminol-
StandardsvolumeInformation,refertothestandard’sDocumentSummaryPageon
the ASTM website. ogy E772.
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G177 − 03 (2008)
3.2 Definitions of Terms Specific to This Standard: water vapor in a vertical column from the ground to the top of
the atmosphere. (Unit: cm or g/cm )
3.2.1 air mass zero (AM0)—describes solar radiation quan-
tities outside the Earth’s atmosphere at the mean Earth-Sun
3.2.10 total ozone—the depth of a column of pure ozone
distance (1 Astronomical Unit). See ASTM E490.
equivalent to the total of the ozone in a vertical column from
thegroundtothetopoftheatmosphere.(Unit:atmosphere-cm)
3.2.2 integrated irradiance E —spectral irradiance in-
λ1−λ2
tegrated over a specific wavelength interval from λ to λ , 3.2.11 wavenumber—a unit of frequency, υ, in units of
1 2
-2 -1
measured in W·m ; mathematically: reciprocal centimeters (symbol cm ) commonly used in place
of wavelength, λ. The relationship between wavelength and
λ2
E 5 E dλ (1)
*
λ12λ2 λ frequency is defined by λυ = c, where c is the speed of light in
λ1
vacuum.Toconvertwavenumbertonanometers, λ·nm=1·10 /
-1
3.2.3 solarirradiance,hemisphericalE —onagivenplane,
H
υ·cm .
thesolarradiantfluxreceivedfromthewithinthe2-πsteradian
field of view of a tilted plane from the portion of the sky dome
4. Technical Basis for the Tables
and the foreground included in the plane’s field of view,
4.1 These tables are modeled data generated using an air
including both diffuse and direct solar radiation.
mass zero (AM0) spectrum based on the extraterrestrial spec-
3.2.3.1 Discussion—For the special condition of a horizon-
trumofofGueymard (1,2)derivedfromKurucz (5),theUnited
tal plane the hemispherical solar irradiance is properly termed
States StandardAtmosphere of 1976 (USSA) referenceAtmo-
global solar irradiance, E . Incorrectly, global tilted, or total
G
sphere (6), the Shettle and Fenn RuralAerosol Profile (7), the
global irradiance is often used to indicate hemispherical
SMARTS2 V. 2.9.2 radiative transfer code. Further details are
irradiance for a tilted plane. In case of a sun-tracking receiver,
provided in X1.3.
this hemispherical irradiance is commonly called global nor-
mal irradiance. The adjective global should refer only to 4.2 The 37° tilted surface was selected as it represents the
average latitude of the contiguous forty-eight states of the
hemispherical solar radiation on a horizontal, not a tilted,
surface. continental U.S., and outdoor exposure testing often takes
place at latitude tilt.
3.2.4 aerosol optical depth (AOD)—the wavelength-
4.3 The documented USSA atmospheric profiles utilized in
dependent total extinction (scattering and absorption) by aero-
the MODTRAN spectral transmission model (6) have been
sols in the atmosphere. This optical depth (also called “optical
used to provide atmospheric properties and concentrations of
thickness”) is defined here at 500 nm.
absorbers.
3.2.4.1 Discussion—See X1.1.
4.4 The SMARTS model Version 2.9.2 is available at
3.2.5 solar irradiance, spectral E —solar irradiance E per
λ
Internet URL: http://rredc.nrel.gov/solar/models/SMARTS.
unit wavelength interval at a given wavelength λ. (Unit: Watts
-2 -1
per square meter per nanometer, W·m ·nm )
4.5 To provide spectral data with a uniform spectral step
size,theAM0spectrumusedinconjunctionwithSMARTS2to
dE
E 5 (2) generate the terrestrial spectrum is slightly different from the
λ
dλ
ASTMextraterrestrialspectrum,ASTME490.BecauseASTM
3.2.6 spectral passband—the effective wavelength interval E490 and SMARTS2 both use the data of Kurucz (5), the
within which spectral irradiance is allowed to pass, as through SMARTS2 and E490 spectra are in excellent agreement
a filter or monochromator. The convolution integral of the although they do not have the same spectral resolution.
spectral passband (normalized to unity at maximum) and the
4.6 The current spectra reflect improved knowledge of
incident spectral irradiance produces the effective transmitted
atmosphericaerosolopticalproperties,transmissionproperties,
irradiance.
and radiative transfer modeling (8).
3.2.6.1 Discussion—Spectral passband may also be referred
4.7 The terrestrial solar spectral in the tables have been
toasthespectralbandwidthofafilterordevice.Passbandsare
computed with a spectral bandwidth equivalent to the spectral
usually specified as the interval between wavelengths at which
resolution of the tables, namely 0.5 nm.
one half of the maximum transmission of the filter or device
occurs, or as full-width at half-maximum, FWHM.
5. Significance and Use
3.2.7 spectral interval—the distance in wavelength units
5.1 Thisstandarddoesnotpurporttoaddressthemeanlevel
between adjacent spectral irradiance data points.
of solar ultraviolet spectral irradiance to which materials will
3.2.8 spectral resolution—the minimum wavelength differ-
be subjected during their useful life. The spectral irradiance
ence between two wavelengths that can be identified unam-
distributions have been chosen to represent a reasonable upper
biguously.
limit for natural solar ultraviolet radiation that ought to be
3.2.8.1 Discussion—In the context of this standard, the considered when evaluating the behavior of materials under
spectral resolution is simply the interval, ∆λ, between spectral
various exposure conditions.
data points, or the spectral interval.
5.2 Absorptance, reflectance, and transmittance of solar
3.2.9 total precipitable water—the depth of a column of energy are important factors in material degradation studies.
water (with a section of 1 cm ) equivalent to the condensed These properties are normally functions of wavelength, which
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G177 − 03 (2008)
require that the spectral distribution of the solar flux be known isshowninFig.1.TheinputneededbySMARTS2togenerate
before the solar-weighted property can be calculated. the spectrum for the prescribed conditions are shown in Table
1.
5.3 The interpretation of the behavior of materials exposed
to either natural solar radiation or ultraviolet radiation from 5.5 SMARTS2 Version 2.9.2 is
...
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